Just take a look at the number of keys you need to maintain. If you’re a homeowner, it’s rare to own more than a handful of keys. If you’re a landlord, however, you’ll need at least a few dozen—one for each of the units in your building.
As you can imagine, managing dozens of keys is not an easy task, especially when keys have a propensity for being misplaced. Luckily, there is a better option than lugging around a key ring: a master key. Read more from this article: http://bit.ly/2vI2BE3